Transformers are used extensively in electrical and electronic applications. Transformers are useful to step voltages up or down, to couple signal energy from one stage to another, and for impedance matching. Transformers are also useful for sensing current and powering electronic trip units for circuit interrupters such as circuit breakers and other electrical distribution devices. Other applications for transformers include magnetic circuits with solenoids and motor stators. Generally, a transformer consists of two or more windings (primary and secondary, etc . . . ) interlinked by a mutual magnetic field. As such, the transformer is used to transfer electric energy from one circuit to another circuit using magnetic induction.
Current transformers are used to monitor current flow in a circuit, such as to detect excessive power consumption and provide a warning signal or disconnect the power supply. The transformer must be protected from potential hazzards in its immediate environment with some type of sealing enclosure. Current transformers, as well as transformers in general, are shape and size specific to the end user's electrical needs and mounting specifications. Accordingly, this presents a unique challenge to designing and manufacturing a transformer and an enclosure therefor which delivers the required electrical performance with the required mounting specifications, all in the confines of a secure enclosure.
Various types of sealing enclosures are currently utilized to protect the transformer from the environment. One means for protecting transformers includes entirely sealing the transformer assembly with an epoxy resin. This is accomplished by pouring the epoxy resin into a molded container which houses the transformer to completely surround and encase the transformer coil with the epoxy resin. Epoxy is utilized because it prevents impact or vibrational shock from affecting the function of the transformer. However, several drawbacks are associated with epoxy encapsulated transformers: (1) using epoxy to encapsulate the transformer is a time consuming process, and (2) the use of epoxy prevents subsequent repairs to the transformer since the transformer is permanently encapsulated by the epoxy.
Another means for encapsulating transformers includes fastening two separate enclosures together. Typically, the enclosure comprises of two housinghalves which are connected by screws. As with an epoxy enclosure, this type of housing also has several drawbacks. One specific drawback is the increased capital investments in tooling required for each different enclosure. Typically, as the electrical specifications change for a specific transformer, the size of the transformer also changes. Accordingly, the enclosure for the transformer must also be modified. It is very common, however, for the change in transformer size to effect the depth of the transformer, and not the width or height. Thus, modifying the depth of a transformer requires modifying the mounting depth of the enclosure which results in the tooling of a new molded enclosure. The cost of new tooling is very expensive.
Accordingly, there is a need for an effective and efficient means for providing a protective enclosure for encapsulating various sizes of transformers, and specifically current transformers. Such an enclosure must not only provide all of the necessary safety features, but should also allow for quick assembly/disassembly of the enclosure and accessibility for repairs of the transformer. Additionally, the enclosure should eliminate the need for new tooling and additional capital expenditures for manufacturing a variety of sizes of transformer enclosures.